Which crystal habit is commonly associated with gem-quality diamonds?

Which crystal habit is commonly associated with gem-quality diamonds?

• A. Octahedron
• B. Cube
• C. Octahedron
• D. Tetrahedron

Answer: (C)

Diamonds come from a crystal system where growth along the {111} planes is most stable, so the natural form that best fits these planes is an octahedron. An octahedron has eight faces that align with those {111} directions, making it the most common rough crystal habit seen in gem-quality diamonds. Because the diamond lattice favors growth along those planes, octahedral outlines tend to appear in natural crystals and guide how cutters approach shaping facets to maximize brilliance. Cube forms, which would rely on {100} planes, are much less common for diamonds, and a tetrahedral outline isn’t the typical dominant habit for gem-quality crystals. So the octahedral shape is the best-known association with diamond crystals.

Diamonds come from a crystal system where growth along the {111} planes is most stable, so the natural form that best fits these planes is an octahedron. An octahedron has eight faces that align with those {111} directions, making it the most common rough crystal habit seen in gem-quality diamonds. Because the diamond lattice favors growth along those planes, octahedral outlines tend to appear in natural crystals and guide how cutters approach shaping facets to maximize brilliance. Cube forms, which would rely on {100} planes, are much less common for diamonds, and a tetrahedral outline isn’t the typical dominant habit for gem-quality crystals. So the octahedral shape is the best-known association with diamond crystals.